Hi everyone, today on the Healing Bench, we have a set of three LED panels. These panels are 18 watts each and were initially used to light up a hallway with a PIR sensor. Interestingly, after about 9 months of occasional use, all three panels failed within a week of each other. The brand in question here is Lambario, and upon noticing the simultaneous failure, I got intrigued and decided it was time to see if I could identify the issue and hopefully fix it.

Since we will be dealing with mains voltage, I can't stress enough the importance of safety when dealing with it. Make sure the power supply is completely disconnected and give adequate time for any internal capacitors to discharge. Capacitors can store charge even when the device is off, posing a risk of an unexpected electric shock. Always double-check that you've discharged the capacitors fully before touching any of the circuitry.

The diagnosis and repair process of the LED panels is more about the intrinsic learning value and the satisfaction of problem-solving than about any commercial repair viability. Tackling such a project offers a hands-on opportunity to deepen our understanding of electronics, refine technical skills, and cultivate patience and precision. The economic benefit of repairing such a panel is trivial compared to the thrill of reviving what was once broken so I invite you to view this not just as a step-by-step guide but as an invitation to embrace the challenges and joys of DIY electronics repair.

Before I jump into the repair process, I must thank PCBWay, the sponsor of this Instructable. Their services in high precision parts, 3D printing, and CNC machining are unmatched, offering tremendous support for projects needing varying component quantities with incredible speed, accuracy, and reliability.

Let's dive in and see if these LED panels can be brought back to life.

Supplies

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Step 1: Opening the LED Panel Driver

The first step was to open up one of the LED panel drivers. With a flathead screwdriver, I gently pried open the back of the case. This exposed the circuitry inside, so I could inspect the driver circuit.

Before poking around the circuits, I touched both legs of the capacitor with the metal tip of the screwdriver to discharge it. Capacitors can hold charge long after the power is off. Discharging is as simple as using a resistor or a screwdriver with an insulated handle to bridge the capacitor's leads, ensuring any stored energy is safely released.

After these precautions, the circuitry was ready to be examined. The driver's interior revealed a layout comprising a fusible resistor and metal oxide varistor at the input, leading to a full bridge rectifier, followed by a smoothing capacitor and a control chip among other components.

There wasn't anything obviously wrong with the driver at first glance so I continued to look for a datasheet of the control chip to understand how it works.

Step 2: Analyzing the Circuit

The control chip 1FYL9t2CC was nowhere to be found. I was unable to find any documents or mentions of it online. It must be some proprietary chip that they might have made custom but based on the layout of the board, I was able to figure out the circuit and understand how it works.

At the heart of it, the incoming supply connects through a fusible resistor and a metal oxide varistor, leading into a full bridge rectifier. This is essentially the first line of defense and the main pathway for converting AC to DC power that the LED panels can use. Just after the rectifier, there lay a capacitor, ready to smooth out the DC output, and a control chip which is critical for regulating the power to the LEDs. Also in view were two resistors that caught my attention that will be important later on.

The choke and output smoothing capacitor worked together to ensure that the power reaching the LEDs was stable and free of spikes that could cause damage or reduce the lifespan of the LEDs. Meanwhile, a resistor was placed strategically to prevent any current from "bleeding" through the LEDs when they should be off.

At this stage, both the capacitors looked intact, with no visible signs of wear or failure, such as bulging or leakage that typically signify a capacitor gone bad. Honestly, everything within the driver seemed perfectly normal, which was both reassuring and vexing. I had hoped for a clear culprit within the driver's circuitry, but it wasn't to be. This pointed me towards a possible problem outside of the driver, shifting my focus to the LED panels themselves.

Step 3: Inspecting the LED Panels

With the driver appearing to function correctly, my suspicion turned to the LED panels. To get a closer look, I had to open one up. These panels were secured in place by punches on the sides. By applying gentle pressure from the back and nudging the outer frame outward, I gradually separated the metal rings from the core housing. This method needed some patience—you don't want to apply too much force and damage the components inside.

Once opened, the panel revealed its internal architecture: a diffuser plate at the front, aimed at evenly spreading the light emitted by the LEDs, followed by a piece of diffused glass and finally, a reflector sitting at the back. This left us with the LED strip, integral to our next phase of troubleshooting, mounted on a metal plate that served both as a support structure and a heat sink to dissipate the heat generated by the LEDs.

Turning my attention to the LED strip, it was a moment of truth; my initial inspection didn’t reveal any immediately visible signs of damage, like burn marks or broken diodes, at least not on the first panel that I opened. I decided to test the LEDs directly, setting my meter to diode mode, I began systematically applying a small voltage across each LED in sequence. The idea was that they should light up when the positive and negative probes are correctly applied, indicating a functional diode.

On the first panel, it turned out that the last pair of LEDs failed and there were two other pairs where only one of the LEDs was working. Having the two LEDS fail, means that the electricity path is terminated and the circuit is open, preventing the rest from working.

Step 4: Diagnosing the Fault

Applying a test voltage across the LEDs in the strip should make them glow faintly if they are functioning correctly. It began promising with the first couple of LEDs lighting up indicating they were working OK but I then started noticing issues.

One LED at a point only lit up faintly, while its parallel partner didn't light up at all. This scenario was peculiar because, theoretically, if one LED in a parallel pair fails, and the other should still function, it will have an increased load as it will carry all of the current alone. This indicated a potential problem but didn't entirely disrupt the circuit.

While a single non-functional LED in a parallel pair didn't halt the operation, pairs of non-functioning LEDs in series did; they acted as breaks in the circuit, preventing the flow of electricity. This is exactly what happened to the last pair of LEDs where none of them lit up when tested.

On the other two panels, there were even visible black dots on the burnt LEDs where even without measuring. you could tell that they were bad.

Step 5: Executing the Fix

The diagnosis pinpointed the specific LEDs on the strip that weren't lighting up. The immediate solution is quite straightforward, just bypass the faulty LEDs to restore the circuit's continuity.

For this task, I prepared some fine wires and my soldering iron, set at 450 degrees Celsius, since the metal backing will suck up a lot of the heat. To remove the LEDs, I basically melted them with the soldering iron, making sure not to apply too much pressure to prevent damage to the tracks on the strip itself.

Once removed, I soldered a piece of wire onto the pads, effectively bypassing the non-functional LEDs and restoring continuity.

Step 6: Testing and Results

To test the repaired panels, I used a dim bulb tester setup. This ingenious device is essentially a safety mechanism that prevents any potential damage to the circuit or explosions in case of a short circuit during testing. By inserting a 100-watt light bulb in series with the load, the bulb acts as a current limiter, allowing safe observation of the circuit's behavior when power is applied.

As the power was switched on, the panels lit up, signifying the initial success of the repair. This also confirmed that the driver circuit was working as designed and I could have ended my endeavor here, but I decided to go a step deeper and figure out how to prevent this issue from happening again.

Step 7: Addressing Underlying Issues

The way these panels are made, almost all of the manufacturers push the LEDs to the maximum of what they can handle. This excessive current is stressing the LEDs, leading to their premature failure. To rectify this, my focus shifted back to the LED driver circuit, aiming to tweak it in a way that could reduce the power output without drastically diminishing its brightness.

The driver essentially controls the flow of power to the LEDs, and by modifying its output characteristics, I could potentially enhance the LED strip's longevity. By reverse engineering the circuit, I was able to figure out that there was a 1.65 Ohm resistor on board, connected to pin 7 that was used to define the current to the LEDs.

I tried several options with the resistors that I had with different results.

In the initial try, I used two 8 Ohm resistors in parallel, to create a 4 Ohm resistor, but with this one, the panel did not light up at all.

Next, I tried using the existing 1.65 Ohm resistor to which I soldered another 1 Ohm resistor and while this worked well, dropping the power to around 10 watts, while power off, the panel was blinking since there seemed to be enough power stored in the capacitor for the chip to think that it needs to start them again.

As a final test, I used 2, 1 Ohm resistors in series and this seemed to work the best. The panel lit up brightly without any issues or noticeable differences in output light.

For a more definitive understanding of the impact of my modifications, I measured the power consumption before and after. Initially drawing around 17 watts, the altered setup showed a reduced consumption of around 14 watts, a direct result of the lowered current flowing through the LEDs.

This reduction in power draw was the goal, aiming to lessen the thermal stress on the LEDs which could potentially extend their lifespan.

Step 8: Conclusion and Next Steps

To sum up, fixing these LED panels turned out to be a great learning experience. We went through diagnosing the problem, figuring out a fix, and even tweaking the circuits to prevent future issues.

The modification of the LED drivers is best done on new panels, so they can have a longer lifespan to not push the LEDs that hard.

If you liked the process or have any questions, feel free to drop a comment below. Keep an eye on and subscribe to my YouTube channel for more projects and fixes coming up. Remember, every repair is a step towards becoming better at solving problems. Thanks for following along, and I hope to see you in the next project.